The Heroku Cedar stack is the current and most performant Heroku platform stack in place. It is based on Ubuntu 11 as the base operating system and delivers a scalable and highly available, fault-tolerant platform for running your Heroku applications.

If your application runs on older Heroku stacks or you are migrating to Heroku, make sure you are using the Cedar stack for your applications. The link at https://devcenter.heroku.com/articles/cedar-migration provides detailed information about how to migrate your app to the Cedar stack to get the best performance and features. If you are running on the older stacks, it makes sense to migrate to the Cedar stack and harness the full power of the Heroku platform.

If you are already on Heroku, you can check the current stack used by your application by logging in to Heroku and going to the specific application folder and typing the following heroku stack command. The * indicates the currently used stack...